/****************************************************************//**
 *
 * @file tftp_server.c
 *
 * @author   Logan Gunthorpe <logang@deltatee.com>
 *           Dirk Ziegelmeier <dziegel@gmx.de>
 *
 * @brief    Trivial File Transfer Protocol (RFC 1350)
 *
 * Copyright (c) Deltatee Enterprises Ltd. 2013
 * All rights reserved.
 *
 ********************************************************************/

/*
 * Redistribution and use in source and binary forms, with or without
 * modification,are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Author: Logan Gunthorpe <logang@deltatee.com>
 *         Dirk Ziegelmeier <dziegel@gmx.de>
 *
 */

/**
 * @defgroup tftp TFTP server
 * @ingroup apps
 *
 * This is simple TFTP server for the lwIP raw API.
 */

#include "lwip/apps/tftp_server.h"

#if LWIP_UDP

#include "lwip/udp.h"
#include "lwip/timeouts.h"
#include "lwip/debug.h"

#define TFTP_MAX_PAYLOAD_SIZE 512
#define TFTP_HEADER_LENGTH    4

#define TFTP_RRQ   1
#define TFTP_WRQ   2
#define TFTP_DATA  3
#define TFTP_ACK   4
#define TFTP_ERROR 5

enum tftp_error
{
    TFTP_ERROR_FILE_NOT_FOUND    = 1,
    TFTP_ERROR_ACCESS_VIOLATION  = 2,
    TFTP_ERROR_DISK_FULL         = 3,
    TFTP_ERROR_ILLEGAL_OPERATION = 4,
    TFTP_ERROR_UNKNOWN_TRFR_ID   = 5,
    TFTP_ERROR_FILE_EXISTS       = 6,
    TFTP_ERROR_NO_SUCH_USER      = 7
};

#include <string.h>

struct tftp_state
{
    const struct tftp_context *ctx;
    void *handle;
    struct pbuf *last_data;
    struct udp_pcb *upcb;
    ip_addr_t addr;
    u16_t port;
    int timer;
    int last_pkt;
    u16_t blknum;
    u8_t retries;
    u8_t mode_write;
};

static struct tftp_state tftp_state;

static void tftp_tmr(void *arg);

static void
close_handle(void)
{
    tftp_state.port = 0;
    ip_addr_set_any(0, &tftp_state.addr);

    if(tftp_state.last_data != NULL)
    {
        pbuf_free(tftp_state.last_data);
        tftp_state.last_data = NULL;
    }

    sys_untimeout(tftp_tmr, NULL);

    if (tftp_state.handle)
    {
        tftp_state.ctx->close(tftp_state.handle);
        tftp_state.handle = NULL;
        LWIP_DEBUGF(TFTP_DEBUG | LWIP_DBG_STATE, ("tftp: closing\n"));
    }
}

static void
send_error(const ip_addr_t *addr, u16_t port, enum tftp_error code, const char *str)
{
    int str_length = strlen(str);
    struct pbuf *p;
    u16_t *payload;

    p = pbuf_alloc(PBUF_TRANSPORT, (u16_t)(TFTP_HEADER_LENGTH + str_length + 1), PBUF_RAM);
    if(p == NULL)
    {
        return;
    }

    payload = (u16_t *) p->payload;
    payload[0] = PP_HTONS(TFTP_ERROR);
    payload[1] = lwip_htons(code);
    MEMCPY(&payload[2], str, str_length + 1);

    udp_sendto(tftp_state.upcb, p, addr, port);
    pbuf_free(p);
}

static void
send_ack(u16_t blknum)
{
    struct pbuf *p;
    u16_t *payload;

    p = pbuf_alloc(PBUF_TRANSPORT, TFTP_HEADER_LENGTH, PBUF_RAM);
    if(p == NULL)
    {
        return;
    }
    payload = (u16_t *) p->payload;

    payload[0] = PP_HTONS(TFTP_ACK);
    payload[1] = lwip_htons(blknum);
    udp_sendto(tftp_state.upcb, p, &tftp_state.addr, tftp_state.port);
    pbuf_free(p);
}

static void
resend_data(void)
{
    struct pbuf *p = pbuf_alloc(PBUF_TRANSPORT, tftp_state.last_data->len, PBUF_RAM);
    if(p == NULL)
    {
        return;
    }

    if(pbuf_copy(p, tftp_state.last_data) != ERR_OK)
    {
        pbuf_free(p);
        return;
    }

    udp_sendto(tftp_state.upcb, p, &tftp_state.addr, tftp_state.port);
    pbuf_free(p);
}

static void
send_data(void)
{
    u16_t *payload;
    int ret;

    if(tftp_state.last_data != NULL)
    {
        pbuf_free(tftp_state.last_data);
    }

    tftp_state.last_data = pbuf_alloc(PBUF_TRANSPORT, TFTP_HEADER_LENGTH + TFTP_MAX_PAYLOAD_SIZE, PBUF_RAM);
    if(tftp_state.last_data == NULL)
    {
        return;
    }

    payload = (u16_t *) tftp_state.last_data->payload;
    payload[0] = PP_HTONS(TFTP_DATA);
    payload[1] = lwip_htons(tftp_state.blknum);

    ret = tftp_state.ctx->read(tftp_state.handle, &payload[2], TFTP_MAX_PAYLOAD_SIZE);
    if (ret < 0)
    {
        send_error(&tftp_state.addr, tftp_state.port, TFTP_ERROR_ACCESS_VIOLATION, "Error occured while reading the file.");
        close_handle();
        return;
    }

    pbuf_realloc(tftp_state.last_data, (u16_t)(TFTP_HEADER_LENGTH + ret));
    resend_data();
}

static void
recv(void *arg, struct udp_pcb *upcb, struct pbuf *p, const ip_addr_t *addr, u16_t port)
{
    u16_t *sbuf = (u16_t *) p->payload;
    int opcode;

    LWIP_UNUSED_ARG(arg);
    LWIP_UNUSED_ARG(upcb);

    if (((tftp_state.port != 0) && (port != tftp_state.port)) ||
            (!ip_addr_isany_val(tftp_state.addr) && !ip_addr_cmp(&tftp_state.addr, addr)))
    {
        send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "Only one connection at a time is supported");
        pbuf_free(p);
        return;
    }

    opcode = sbuf[0];

    tftp_state.last_pkt = tftp_state.timer;
    tftp_state.retries = 0;

    switch (opcode)
    {
    case PP_HTONS(TFTP_RRQ): /* fall through */
    case PP_HTONS(TFTP_WRQ):
    {
        const char tftp_null = 0;
        char filename[TFTP_MAX_FILENAME_LEN];
        char mode[TFTP_MAX_MODE_LEN];
        u16_t filename_end_offset;
        u16_t mode_end_offset;

        if(tftp_state.handle != NULL)
        {
            send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "Only one connection at a time is supported");
            break;
        }

        sys_timeout(TFTP_TIMER_MSECS, tftp_tmr, NULL);

        /* find \0 in pbuf -> end of filename string */
        filename_end_offset = pbuf_memfind(p, &tftp_null, sizeof(tftp_null), 2);
        if((u16_t)(filename_end_offset - 2) > sizeof(filename))
        {
            send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "Filename too long/not NULL terminated");
            break;
        }
        pbuf_copy_partial(p, filename, filename_end_offset - 2, 2);

        /* find \0 in pbuf -> end of mode string */
        mode_end_offset = pbuf_memfind(p, &tftp_null, sizeof(tftp_null), filename_end_offset + 1);
        if((u16_t)(mode_end_offset - filename_end_offset) > sizeof(mode))
        {
            send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "Mode too long/not NULL terminated");
            break;
        }
        pbuf_copy_partial(p, mode, mode_end_offset - filename_end_offset, filename_end_offset + 1);

        tftp_state.handle = tftp_state.ctx->open(filename, mode, opcode == PP_HTONS(TFTP_WRQ));
        tftp_state.blknum = 1;

        if (!tftp_state.handle)
        {
            send_error(addr, port, TFTP_ERROR_FILE_NOT_FOUND, "Unable to open requested file.");
            break;
        }

        LWIP_DEBUGF(TFTP_DEBUG | LWIP_DBG_STATE, ("tftp: %s request from ", (opcode == PP_HTONS(TFTP_WRQ)) ? "write" : "read"));
        ip_addr_debug_print(TFTP_DEBUG | LWIP_DBG_STATE, addr);
        LWIP_DEBUGF(TFTP_DEBUG | LWIP_DBG_STATE, (" for '%s' mode '%s'\n", filename, mode));

        ip_addr_copy(tftp_state.addr, *addr);
        tftp_state.port = port;

        if (opcode == PP_HTONS(TFTP_WRQ))
        {
            tftp_state.mode_write = 1;
            send_ack(0);
        }
        else
        {
            tftp_state.mode_write = 0;
            send_data();
        }

        break;
    }

    case PP_HTONS(TFTP_DATA):
    {
        int ret;
        u16_t blknum;

        if (tftp_state.handle == NULL)
        {
            send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "No connection");
            break;
        }

        if (tftp_state.mode_write != 1)
        {
            send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "Not a write connection");
            break;
        }

        blknum = lwip_ntohs(sbuf[1]);
        pbuf_header(p, -TFTP_HEADER_LENGTH);

        ret = tftp_state.ctx->write(tftp_state.handle, p);
        if (ret < 0)
        {
            send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "error writing file");
            close_handle();
        }
        else
        {
            send_ack(blknum);
        }

        if (p->tot_len < TFTP_MAX_PAYLOAD_SIZE)
        {
            close_handle();
        }
        break;
    }

    case PP_HTONS(TFTP_ACK):
    {
        u16_t blknum;
        int lastpkt;

        if (tftp_state.handle == NULL)
        {
            send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "No connection");
            break;
        }

        if (tftp_state.mode_write != 0)
        {
            send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "Not a read connection");
            break;
        }

        blknum = lwip_ntohs(sbuf[1]);
        if (blknum != tftp_state.blknum)
        {
            send_error(addr, port, TFTP_ERROR_UNKNOWN_TRFR_ID, "Wrong block number");
            break;
        }

        lastpkt = 0;

        if (tftp_state.last_data != NULL)
        {
            lastpkt = tftp_state.last_data->tot_len != (TFTP_MAX_PAYLOAD_SIZE + TFTP_HEADER_LENGTH);
        }

        if (!lastpkt)
        {
            tftp_state.blknum++;
            send_data();
        }
        else
        {
            close_handle();
        }

        break;
    }

    default:
        send_error(addr, port, TFTP_ERROR_ILLEGAL_OPERATION, "Unknown operation");
        break;
    }

    pbuf_free(p);
}

static void
tftp_tmr(void *arg)
{
    LWIP_UNUSED_ARG(arg);

    tftp_state.timer++;

    if (tftp_state.handle == NULL)
    {
        return;
    }

    sys_timeout(TFTP_TIMER_MSECS, tftp_tmr, NULL);

    if ((tftp_state.timer - tftp_state.last_pkt) > (TFTP_TIMEOUT_MSECS / TFTP_TIMER_MSECS))
    {
        if ((tftp_state.last_data != NULL) && (tftp_state.retries < TFTP_MAX_RETRIES))
        {
            LWIP_DEBUGF(TFTP_DEBUG | LWIP_DBG_STATE, ("tftp: timeout, retrying\n"));
            resend_data();
            tftp_state.retries++;
        }
        else
        {
            LWIP_DEBUGF(TFTP_DEBUG | LWIP_DBG_STATE, ("tftp: timeout\n"));
            close_handle();
        }
    }
}

/** @ingroup tftp
 * Initialize TFTP server.
 * @param ctx TFTP callback struct
 */
err_t
tftp_init(const struct tftp_context *ctx)
{
    err_t ret;

    struct udp_pcb *pcb = udp_new_ip_type(IPADDR_TYPE_ANY);
    if (pcb == NULL)
    {
        return ERR_MEM;
    }

    ret = udp_bind(pcb, IP_ANY_TYPE, TFTP_PORT);
    if (ret != ERR_OK)
    {
        udp_remove(pcb);
        return ret;
    }

    tftp_state.handle    = NULL;
    tftp_state.port      = 0;
    tftp_state.ctx       = ctx;
    tftp_state.timer     = 0;
    tftp_state.last_data = NULL;
    tftp_state.upcb      = pcb;

    udp_recv(pcb, recv, NULL);

    return ERR_OK;
}

#endif /* LWIP_UDP */
